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Posted to mapreduce-dev@hadoop.apache.org by "Ted Yu (JIRA)" <ji...@apache.org> on 2014/04/25 22:41:18 UTC

[jira] [Created] (MAPREDUCE-5861) LocalContainerLauncher does not atomically update volatile variable finishedSubMaps

Ted Yu created MAPREDUCE-5861:
---------------------------------

             Summary: LocalContainerLauncher does not atomically update volatile variable finishedSubMaps
                 Key: MAPREDUCE-5861
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5861
             Project: Hadoop Map/Reduce
          Issue Type: Bug
            Reporter: Ted Yu
            Priority: Minor


Around line 374:
{code}
          if (++finishedSubMaps == numMapTasks) {
            doneWithMaps = true;
          }
{code}
The increment of finishedSubMaps is not atomic.

See the answer to http://stackoverflow.com/questions/9749746/what-is-the-difference-of-atomic-volatile-synchronize .

AtomicInteger can be used to achieve atomicity.



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